<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
       .parent{
           width: 200px;
           height: 200px;
           background: red;
           position: relative;
           left:100px;  
           top: 100px;
       }
       .child{
           width: 100px;
           height: 100px;
           background: blue;
           position: absolute;
           /*position:absolute 的left,top它是相对于最近的给了定位的父元素*/
           right:-20px;
           bottom:0;
       }
    </style>
</head>
<body>
   <!--position:absolute,relative,fixed-->
   <!--position:relative 就是元素在页面上正常的位置
     left,top
-->
   <div class="parent">
     <div class="child">
     </div>
   </div>
   <p>hello world</p>
</body>
</html>